In general, a refrigerant compressor is applied to a vapor compression type refrigerating cycle (hereinafter, referred to as ‘refrigerating cycle’), such as a refrigerator or an air conditioner. A constant-speed type compressor driven at constant speed and an inverter type compressor capable of controlling rotation speed have been introduced as the refrigerant compressor.
The refrigerant compressors are categorized as follows. A refrigerant compressor, in which a driving motor (typically, an electric motor) and a compression part operated by the driving motor are all installed in an inner space of a hermetic casing, is referred to as a hermetic type compressor, and a compressor of which the driving motor is separately installed outside the casing is referred to as an open type compressor. Home or commercial cooling apparatuses usually employ the hermetic type compressor. The refrigerant compressors may be categorized into a reciprocating type, a scroll type, a rotary type and the like according to a refrigerant compression mechanism.
The rotary compressor compresses a refrigerant by use of a rolling piston eccentrically rotating in a compression space of a cylinder and a vane contacted with a rolling piston for partitioning the compression space of the cylinder into a suction chamber and a discharge chamber. In recent time, a variable capacity type rotary compressor capable of varying a cooling capacity of the compressor according to the change in a load has been introduced. Well-known technologies for varying the cooling capacity of the compressor include applying an inverter motor, and varying a volume of a compression chamber by bypassing part of a compressed refrigerant out of a cylinder. However, for employing the inverter motor, a driver for driving the inerter motor is about 10 times as expensive as a driver of a constant-speed motor, thereby rising a fabrication cost of the compressor. On the other hand, for bypassing the refrigerant, a piping system becomes complicated and accordingly a flow resistance of the refrigerant is increased, thereby lowering efficiency of the compressor.
Considering such drawbacks, a so-called modulation type variable capacity rotary compressor, in which at least one or more cylinders are provided and at least one of them is allowed for idling, has been introduced. The modulation type variable capacity rotary compressors may be categorized into a compressor employing a forward pressure mechanism and a compressor employing a recoil pressure mechanism according to a vane restriction method. For instance, the compressor employing the forward pressure mechanism is configured such that a discharge pressure is applied via a suction hole and accordingly a vane is pushed backwardly by pressure of a compression space so as to be restricted, while the compressor employing the recoil pressure mechanism is configured such that a back pressure of suction pressure or discharge pressure is applied to a rear side of the vane so as to selectively restrict the vane. The present invention is applied to a modulation type variable capacity rotary compressor (hereinafter, referred to as ‘rotary compressor’) employing the recoil pressure mechanism.
The related art rotary compressor uses a connection tube between a connection pipe of a mode switching unit and a rear side of a vane when coupling the mode switching unit in order to apply a back pressure to the rear side of the vane. However, if a diameter of the connection tube and a diameter of a hole in which the connection tube is inserted are not appropriately designated, a leakage of refrigerant may occur. For example, if a great gap exists between the connection tube and the hole, a refrigerant may be leaked through the gap. On the other hand, if the connection tube and the hole are excessively adhered to each other, upon press-fitting the connection tube, the connection tube having relatively low intensity is scratched or crushed, thereby causing the leakage of refrigerant.